This invention relates to a seat hinge, and more particularly, to a seat hinge structure for a motor vehicle employing an internal inertia sensitive element which prevents articulation of the hinge in certain conditions.
Passenger cars having two side doors and a rear occupant seating area generally must be provided with a mechanism which permits the front seat back to be rotated forward, thereby providing sufficient clearance for access to the rear seating area, and to permit entrance to and egress from the rear seating area by passengers. In the past, manually operated hinge mechanisms were prevalent. These devices required the passenger to manually actuate a lever or other mechanism in order to unlatch the seat back, thereby allowing it to be swung forward. Latching mechanisms are necessary in order to comply with Federal Motor Vehicle Safety Standards (FMVSS) which require that the front seat back be held in a nearly vertical position when the vehicle is subjected to sudden deceleration, as would be experienced during a frontal impact. The intent of these requirements is to prevent the seat back from striking the front seat occupants in such conditions. In an effort to improve comfort and convenience of motor vehicles, manufacturers have recently provided inertia sensitive seat back hinge mechanisms. These devices employ an internal inertia sensitive element which, when subjected to high rates of deceleration, causes the seat back to be locked, thereby preventing it from moving forward due to the force of such deceleration. Under normal circumstances, however, the rear seat passenger may simply push the front seat back forward without first actuating a release lever.
An additional customer feature which is being provided in modern motor vehicles in increasing numbers are reclining devices which permit the angle of the front seat back relative to the seat bottom to be changed in accordance with the desires of the seat occupant.
Many seat back hinge mechanisms having an inertia sensitive latch and a reclining feature have been heretofore proposed and implemented. One such design, which is described by U.S. Pat. No. 4,372,610, issued on Feb. 8, 1983, to A. J. Fisher III, et al, which is assigned to the assignee of this application, employs a quadrant attached to the lower hinge structure and features an internal arcuate aperture through which a pin affixed to the upper hinge structure passes as the seat back is moved between normal and forward positions. The quadrant according to the previously mentioned patent, however, presents a protruding edge surface toward the rear seat area when the seat back is rotated forward. This edge surface is objectionable in that rear seat occupants could contact it while entering or egressing the rear seat area. This edge surface also prevents the application of interior trim fabrics over this area due to the potential for wearing or tearing of the trim.
The design according to the previously cited U.S. patent also includes a rolling weight type inertia sensor. This sensor employs a disc shaped element which rolls along an enclosed path when subjected to deceleration forces. Motor vehicle manufacturers, however, desire to avoid such rolling weight inertia sensors since they believe that these devices may be a source of noise and rattle problems as the vehicle is subjcted to road induced vibrations.
It is therefore a principal object of this invention to provide an improved motor vehicle seat hinge structure having a quadrant component which does not present an objectional protruding edge surface to rear seat occupants when the front seat is moved forward. It is another principal object of this invention to provide an inertia sensor device which does not employ a rolling weight.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates upon a reading of the described preferred embodiments of this invention taken in conjunction with the accompanying drawings.